var onlyTap = {
    tap: function(dom, callback) {
        var startX, startY;
        var st;
        //开始触屏瞬间
        dom.addEventListener('touchstart', function(event) {
                if (event.targetTouches.length > 1) {
                    return;
                }
                st = Date.now();
                startX = event.targetTouches[0].clientX;
                startY = event.targetTouches[0].clientY;
            })
            //离开屏幕瞬间
        dom.addEventListener('touchend', function(event) {
            if (Date.now() - st > 200) {
                return;
            }
            var endX = event.changedTouches[0].clientX;
            var endY = event.changedTouches[0].clientY;
            if (Math.abs(endX - startX) > 6 || Math.abs(endY - startY) > 6) {
                return;
            }
            callback && callback(event);
        })
    }
};